I have it running in a CT, utilising 3% of 2 cores while monitoring an 80 device/services homelab.
I think it's a great app and the only thing I don't like is that it spams the system logs of all the monitored Proxmox nodes.
Indeed it has improved since July. Back then I had the same experience.
I tried it again today with 22 Nodes and 506 VMs and here's the CPU usage of the Pulse VM so far.